In order to minimize membrane fouling in electrochemical systems using ion exchange membranes, we are having developed monovalent cation selective membranes prepared by a pore-filled technique. The transparent pore-filled membranes indicated that the porous PE substrate was successfully filled with polymer electrolyte by UV irradiation. The weight ratio of anion polymer electrolyte layer was 0.20 and 0.59. The dimensional stability and area resistance of the monovalent selective membranes increased with the weight content of anion polymer electrolyte. Lab-made monovalent selective membranes showed low ion permeability. However, they have similar permeability ratio between NaCl and MgCl2 (or CaCl2) than CMV, and the flux of the sample was slightly higher than commercial membrane. Further characterizations of the resulting membranes will be performed, and reported in the near future.